linux-kernel - Re: 1808d65b55 ("asm-generic/tlb: Remove arch_tlb*_mmu()"): BUG: KASAN: stack-out-of-bounds in __change_page_attr_set

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Message-ID: <721948C9-0E56-4E70-B9C5-58F0A4A5C126@vmware.com>
Date:   Fri, 12 Apr 2019 19:42:37 +0000
From:   Nadav Amit <namit@...are.com>
To:     Peter Zijlstra <peterz@...radead.org>
CC:     kernel test robot <lkp@...el.com>, LKP <lkp@...org>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will.deacon@....com>,
        Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Dave Hansen <dave.hansen@...el.com>
Subject: Re: 1808d65b55 ("asm-generic/tlb: Remove arch_tlb*_mmu()"):  BUG:
 KASAN: stack-out-of-bounds in __change_page_attr_set_clr

> On Apr 12, 2019, at 11:19 AM, Peter Zijlstra <peterz@...radead.org> wrote:
> 
> On Fri, Apr 12, 2019 at 03:11:22PM +0000, Nadav Amit wrote:
>>> On Apr 12, 2019, at 4:17 AM, Peter Zijlstra <peterz@...radead.org> wrote:
> 
>>> To clarify, 'that' is Nadav's patch:
>>> 
>>> 515ab7c41306 ("x86/mm: Align TLB invalidation info")
>>> 
>>> which turns out to be the real problem.
>> 
>> Sorry for that. I still think it should be aligned, especially with all the
>> effort the Intel puts around to avoid bus-locking on unaligned atomic
>> operations.
> 
> No atomics anywhere in sight, so that's not a concern.

You are right. I still think that at least TLB-wise it should be better to
have the argument off-stack. I’ll try to run some experiments, based on
your feedback, and send a patch on top of your revert.

Sorry for the mess, again.